BackgroundImbalances of gut microbiota composition are linked to a range of metabolic perturbations. In the present study, we examined the gut microbiota of women with gestational diabetes mellitus (GDM) and normoglycaemic pregnant women in late pregnancy and about 8 months postpartum.MethodsGut microbiota profiles of women with GDM (n = 50) and healthy (n = 157) pregnant women in the third trimester and 8 months postpartum were assessed by 16S rRNA gene amplicon sequencing of the V1-V2 region. Insulin and glucose homeostasis were evaluated by a 75 g 2-h oral glucose tolerance test during and after pregnancy.ResultsGut microbiota of women with GDM was aberrant at multiple levels, including phylum and genus levels, compared with normoglycaemic pregnant women. Actinobacteria at phylum level and Collinsella, Rothia and Desulfovibrio at genus level had a higher abundance in the GDM cohort. Difference in abundance of 17 species-level operational taxonomic units (OTUs) during pregnancy was associated with GDM. After adjustment for pre-pregnancy body mass index (BMI), 5 of the 17 OTUs showed differential abundance in the GDM cohort compared with the normoglycaemic pregnant women with enrichment of species annotated to Faecalibacterium and Anaerotruncus and depletion of species annotated to Clostridium (sensu stricto) and to Veillonella. OTUs assigned to Akkermansia were associated with lower insulin sensitivity while Christensenella OTUs were associated with higher fasting plasma glucose concentration. OTU richness and Shannon index decreased from late pregnancy to postpartum regardless of metabolic status. About 8 months after delivery, the microbiota of women with previous GDM was still characterised by an aberrant composition. Thirteen OTUs were differentially abundant in women with previous GDM compared with women with previous normoglycaemic pregnancy.ConclusionGDM diagnosed in the third trimester of pregnancy is associated with a disrupted gut microbiota composition compared with normoglycaemic pregnant women, and 8 months after pregnancy, differences in the gut microbiota signatures are still detectable. The gut microbiota composition of women with GDM, both during and after pregnancy, resembles the aberrant microbiota composition reported in non-pregnant individuals with type 2 diabetes and associated intermediary metabolic traits.Electronic supplementary materialThe online version of this article (10.1186/s40168-018-0472-x) contains supplementary material, which is available to authorized users.

Objective: To assess the in¯uence of smoking on serum parathyroid hormone (PTH), serum vitamin D metabolites, serum ionized calcium, serum phosphate, and biochemical markers of bone turnover in a cohort of 510 healthy Danish perimenopausal women. Design: A cross-sectional study. Setting: Copenhagen, Denmark. Subjects: Five-hundred-and-ten healthy women aged 45 ± 58 y, included 3 ± 24 months after last menstrual bleeding. None were using hormone replacement therapy. Methods: The women were grouped according to their current smoking status. The two groups were compared with regard to serum levels of 25-hydroxyvitamin D (25OHD) and 1,25-dihydroxyvitamin D (1,25-(OH) 2 D), intact PTH, ionized calcium and phosphate, osteocalcin, as well as urine pyridinolines. Bone mineral density (BMD) was measured with DEXA-scans. Multiple regression analyses were performed to detect the effect of potentially confounding lifestyle factors, such as calcium and vitamin D intakes, alcohol and coffee consumption, sunbathing, and physical exercise. Results: Fifty percent were current smokers. Smokers had signi®cantly reduced levels of serum 25OHD (P 0.02), 1,25(OH) 2 D (P 0.001), and PTH (P`0.001). There was no difference in serum ionized calcium between smokers and non-smokers. We found a negative effect of smoking on serum osteocalcin (P 0.01), while urinary pyridinolines were similar in the two groups. The small differences in lifestyle between the two groups could not explain these ®ndings. Smokers had small but signi®cant reductions in bone mineral density. Conclusions: Smoking has a signi®cant effect on calcium and vitamin D metabolism, which is not likely to be explained by other confounding lifestyle factors. The depression of the vitamin D-PTH system seen among smokers may represent another potential mechanism for the deleterious effects of smoking on the skeleton, and may contribute to the reported risk of osteoporosis among smokers.

Many cells coordinate their activities by transmitting rises in intracellular calcium from cell to cell. In nonexcitable cells, there are currently two models for intercellular calcium wave propagation, both of which involve release of inositol trisphosphate (IP3)- sensitive intracellular calcium stores. In one model, IP3 traverses gap junctions and initiates the release of intracellular calcium stores in neighboring cells. Alternatively, calcium waves may be mediated not by gap junctional communication, but rather by autocrine activity of secreted ATP on P2 purinergic receptors. We studied mechanically induced calcium waves in two rat osteosarcoma cell lines that differ in the gap junction proteins they express, in their ability to pass microinjected dye from cell to cell, and in their expression of P2Y2 (P2U) purinergic receptors. ROS 17/2.8 cells, which express the gap junction protein connexin43 (Cx43), are well dye coupled, and lack P2U receptors, transmitted slow gap junction-dependent calcium waves that did not require release of intracellular calcium stores. UMR 106-01 cells predominantly express the gap junction protein connexin 45 (Cx45), are poorly dye coupled, and express P2U receptors; they propagated fast calcium waves that required release of intracellular calcium stores and activation of P2U purinergic receptors, but not gap junctional communication. ROS/P2U transfectants and UMR/Cx43 transfectants expressed both types of calcium waves. Gap junction–independent, ATP-dependent intercellular calcium waves were also seen in hamster tracheal epithelia cells. These studies demonstrate that activation of P2U purinergic receptors can propagate intercellular calcium, and describe a novel Cx43-dependent mechanism for calcium wave propagation that does not require release of intracellular calcium stores by IP3. These studies suggest that gap junction communication mediated by either Cx43 or Cx45 does not allow passage of IP3 well enough to elicit release of intracellular calcium stores in neighboring cells.

No abstract

The primary goal of this cross-sectional in vivo study was to assess peripheral bone microarchitecture, bone strength, and bone remodeling in adult type 1 diabetes (T1D) patients with and without diabetic microvascular disease (MVDþ and MVD-, respectively) and to compare them with age-, gender-, and height-matched healthy control subjects (CoMVDþ and CoMVD-, respectively). The secondary goal was to assess differences in MVD-and MVDþ patients. Fifty-five patients with T1DM (MVDþ group: n ¼ 29) were recruited from the Funen Diabetes Database. Dual-energy X-ray absorptiometry (DXA), high-resolution peripheral quantitative computed tomography (HRpQCT) of the ultradistal radius and tibia, and biochemical markers of bone turnover were performed in all participants. There were no significant differences in HR-pQCT parameters between MVD-and CoMVD-subjects. In contrast, MVDþ patients had larger total and trabecular bone areas (p ¼ 0.04 and p ¼ 0.02, respectively), lower total, trabecular, and cortical volumetric bone mineral density (vBMD) (p < 0.01, p < 0.04, and p < 0.02, respectively), and thinner cortex (p ¼ 0.03) at the radius, and lower total and trabecular vBMD (p ¼ 0.01 and p ¼ 0.02, respectively) at the tibia in comparison to CoMVDþ. MVDþ patients also exhibited lower total and trabecular vBMD (radius p ¼ 0.01, tibia p < 0.01), trabecular thickness (radius p ¼ 0.01), estimated bone strength, and greater trabecular separation (radius p ¼ 0.01, tibia p < 0.01) and network inhomogeneity (radius p ¼ 0.01, tibia p < 0.01) in comparison to MVD-patients. These differences remained significant after adjustment for age, body mass index, gender, disease duration, and glycemic control (average glycated hemoglobin over the previous 3 years). Although biochemical markers of bone turnover were significantly lower in MVDþ and MVD-groups in comparison to controls, they were similar between the MVDþ and MVD-groups. The results of our study suggest that the presence of MVD was associated with deficits in cortical and trabecular bone vBMD and microarchitecture that could partly explain the excess skeletal fragility observed in these patients.

This study examined the effect of recreational football and resistance training on bone mineral density (BMD) and bone turnover markers (BTMs) in elderly men. Twenty-six healthy sedentary men (age 68.2 ± 3.2 years) were randomized into three groups: football (F; n = 9) and resistance training (R; n = 9), completing 45-60 min training two to three times weekly, and inactive controls (C; n = 8). Before, after 4 months, and after 12 months, BMD in proximal femur (PF) and whole body (WB) were determined together with plasma osteocalcin (OC), procollagen type-1 amino-terminal propeptide (P1NP), and carboxy-terminal type-1 collagen crosslinks (CTX-1). In F, BMD in PF increased up to 1.8% (P < 0.05) from 0 to 4 months and up to 5.4% (P < 0.001) from 0 to 12 months; WB-BMD remained unchanged. After 4 and 12 months of football, OC was 45% and 46% higher (P < 0.001), and P1NP was 41% and 40% higher (P < 0.001) than at baseline, respectively. After 12 months, CTX-1 showed a main effect of 43% (P < 0.05). In R and C, BMD and BTM remained unchanged. In conclusion, 4 months of recreational football for elderly men had an osteogenic effect, which was further developed after 12 months, whereas resistance training had no effect. The anabolic response may be due to increased bone turnover, especially improved bone formation.

Aims/hypothesis Individuals with type 2 diabetes have an altered bacterial composition of their gut microbiota compared with non-diabetic individuals. However, these alterations may be confounded by medication, notably the blood-glucose-lowering biguanide, metformin. We undertook a clinical trial in healthy and previously drug-free men with the primary aim of investigating metformin-induced compositional changes in the non-diabetic state. A secondary aim was to examine whether the pre-treatment gut microbiota was related to gastrointestinal adverse effects during metformin treatment. Methods Twenty-seven healthy young Danish men were included in an 18-week one-armed crossover trial consisting of a pre-intervention period, an intervention period and a post-intervention period, each period lasting 6 weeks. Inclusion criteria were men of age 18–35 years, BMI between 18.5 kg/m 2 and 27.5 kg/m 2 , HbA 1c < 39 mmol/mol (5.7%) and plasma creatinine within the normal range. No prescribed medication, including antibiotics, for 2 months prior to recruitment were allowed and no previous gastrointestinal surgery, discounting appendectomy or chronic illness requiring medical treatment. During the intervention the participants were given metformin up to 1 g twice daily. Participants were examined five times in the fasting state with blood sampling and recording of gastrointestinal symptoms. Examinations took place at Frederiksberg Hospital, Denmark before and after the pre-intervention period, halfway through and immediately after the end of intervention and after the wash-out period. Faecal samples were collected at nine evenly distributed time points, and bacterial DNA was extracted and subjected to 16S rRNA gene amplicon sequencing in order to evaluate gut microbiota composition. Subjective gastrointestinal symptoms were reported at each visit. Results Data from participants who completed visit 1 ( n =23) are included in analyses. For the primary outcome the relative abundance of 11 bacterial genera significantly changed during the intervention but returned to baseline levels after treatment cessation. In line with previous reports, we observed a reduced abundance of Intestinibacter spp. and Clostridium spp., as well as an increased abundance of Escherichia/Shigella spp. and Bilophila wadsworthia . The relative abundance at baseline of 12 bacterial genera predicted self-reported gastrointestinal adverse effects. Conclusions/interpretation Intake of metformin changes the gut microbiota composition in normoglycaemic young men. The microbiota changes induced by metformin extend and validate previous reports in individuals with type 2 diabetes. Secondary analyses suggest that pre-treatment gut microbiota composit...

Signaling between osteoblasts and osteoclasts is important in bone homeostasis. We previously showed that human osteoblasts propagate intercellular calcium signals via two mechanisms: autocrine activation of P2Y receptors, and gap junctional communication. In the current work we identified mechanically induced intercellular calcium signaling between osteoblasts and osteoclasts and among osteoclasts. Intercellular calcium responses in osteoclasts required P2 receptor activation but not gap junctional communication. Pharmacological studies and reverse transcriptase-PCR amplification demonstrated that human osteoclasts expressed functional P2Y1 receptors, but, unexpectedly, desensitization of P2Y1 did not block calcium signaling to osteoclasts. We also found that osteoclasts expressed functional P2X7 receptors and showed that pharmacological inhibition of these receptors blocked calcium signaling to osteoclasts. Thus these studies show that calcium signaling between osteoblasts and osteoclasts occurs via activation of P2 receptors, but that different families of P2 receptors are required for calcium signaling in these two cell types. Intercellular calcium signaling among bone cells is therefore amenable to pharmacological manipulation that will specifically affect only bone-forming or bone-resorbing cells. P2 receptors may be important drug targets for the modulation of bone turnover.Osteoclasts are the cells responsible for bone resorption, whereas osteoblasts deposit new bone throughout a lifetime. Bone resorption and formation are coordinated, and in adult life are maintained in a balance, so that no significant bone loss occurs. In later life, especially in women after menopause, osteoclast activity is increased relative to osteoblast activity, and this unbalanced cellular activity causes increased relative bone resorption, and in turn, bone loss and osteoporosis. Both endocrine and paracrine factors modulate osteoclast activity, including calciotropic, growth, sex, and adrenal hormones as well as cytokines, growth factors, electrolytes, and mechanical forces. Most of these paracrine and endocrine factors affect osteoclast activity indirectly, acting on osteoblasts. Thus, boneresorptive signals must be transmitted from osteoblasts to osteoclasts via mechanisms of cell-to-cell communication between the two lineages.We have previously shown that mechanical stimulation of human osteoblasts in vitro generates a calcium signal that is communicated to other osteoblasts (1, 2). The propagation of this signal involves two different mechanisms. One is the autocrine action of ATP on plasma membrane purinergic receptors of the P2Y subtype, and the other involves the passage of a soluble messenger through gap junctions, leading to influx of extracellular calcium.Recent studies have revealed the presence of nucleotide receptors in osteoclasts.1 ATP can act on two different classes of receptors. The P2Y receptors are G-protein-coupled and stimulate phospholipases, subsequently activating the inositol 1,4,5-triphosphate pathw...